1. Field of the Invention
The present invention relates to a method and apparatus for cosmetic reduction of vascular skin blemishes by means of thermolysis using laser irradiation.
2. State of the Art
Vascular irregularities below the surface of the skin can cause visible skin blemishes such as the conditions commonly referred to as Portwine stains, Naevus, Telangiectasia, Strawberry Haemangioma and Thread veins. It has become common practice to cosmetically reduce and preferably remove such vascular blemishes using techniques known as selective thermolysis in which pulsed laser light of a pre-selected wavelength incident on and passing through the skin of a patient is specifically absorbed by a target vascular irregularity lesion leading to xe2x80x9ccoagulation necrosisxe2x80x9d which results in a cosmetic normalising of the colour or tint of the visible blemish with the surrounding skin. Typically a flash lamp pumped dye laser has been utilised emitting light at a wavelength of between 570 nm-600 nm at typical output energy levels of 5-15 J/cm2 with pulse durations in the range 100-600 micro-seconds.
In known selective thermolysis techniques, only a relatively small proportion of the volume of individual blood vessels (depending on the size of the vessels, which can be from 5 microns to 2 mm) comprising the vascular irregularity lesion is heated to thermolysis temperature during the laser pulse. The thermolysis effect is therefore limited to a localised volume of the blood vessels and reduces the probability of the blemish being removed by the treatment.
The present invention seeks to alleviate the above-mentioned difficulty.
According to a first aspect, the invention provides a method of cosmetically reducing a vascular blemish at or below the surface of mammalian skin, which method comprises directing laser radiation to converge toward said blemish from a plurality of different directions, thereby to cause selective thermolysis of blood vessels comprising said vascular blemish.
Because the vessels comprising the blemish are below the surface of the skin, the directed laser radiation is arranged to converge below the surface of the skin. Irradiating the vascular blemish from a plurality of different directions rather than from a single direction only (usually normal to the skin) as with conventional thermolysis techniques, causes a larger volume of individual vessels comprising the vascular blemish to be heated, thereby increasing the average vessel temperature and hence increasing the likelihood of complete or substantial removal of the blemish.
It is preferred that a plurality of substantially linear paths of radiation are provided, each preferably comprising a separate beam, being arrange to converge toward the vascular blemish. Preferably the respective paths or beams are angularly spaced relatively to one another. Desirably, one of the beams or paths is directed normally to the skin of the patient at least one further beam or path being directed at an inclined angle relative to the skin of the patient.
Advantageously, the laser radiation is directed to converge from the plurality of different directions effectively simultaneously. Desirably the directed radiation is pulsed preferably having a pulse duration in the range 100 to 600 micro-seconds.
In a first embodiment of method according to the invention, the laser radiation may comprise a primary beam which is split into a plurality of individual beams which are subsequently directed to converge on the vascular blemish. Alternatively, separate beams may be used, each from a separate source.
It is preferred that the laser radiation converging from the plurality of directions is of the same wavelength (and preferably the same intensity) from each direction. Each of the converging laser beams are therefore effectively identical.
According to a second aspect of the invention, there is provided a laser apparatus for use in selective thermolysis techniques, the apparatus comprising means for directing a laser radiation to converge from a plurality of different directions at a zone of convergence spaced from the apparatus.
It is preferred that the apparatus is arranged to produce a plurality of beams each directed along a respective substantially linear path, the beams being angularly spaced from one another to converge at the zone of convergence.
Advantageously, the beams are arranged to be of substantially the same wavelength, and also preferably of substantially the same intensity.
In one embodiment, apparatus according to the invention may comprise division means for dividing the plurality of laser beams from a primary beam. The division means preferably comprises optical means which may include mirrors and/or beam splitters and/or optical prisms. Desirably, focusing means is provided to focus each beam at the convergence zone. Typically the focusing means comprises a focusing lens.
It is preferred that in certain embodiments modification means is provided to modify the configuration of the beams for example by providing that the focusing means is arranged to focus the respective beam to a line rather than a point or spot. An at least partially cylindrical optic lens is preferably provided for this purpose.
It is believed that laser apparatus for use in selective thermolysis techniques and comprising focusing means arranged to focus a laser beam to a line is inventive per se. This is particularly useful where the target blemish for photothermolysis is substantially linear such as, for example, a thread vein.
In an alternative embodiment, the apparatus may comprise discrete laser sources arranged to produce each respective laser beam.
In either embodiment, it is preferred that pulsation means is provided to pulse the laser radiation.
Specific embodiments of the invention will now be further described by way of example only, and with reference to the accompanying drawings.